As a means of connecting an electrode terminal of a tabular display device having liquid crystals or electro-luminescent elements and a driving electronic circuit board (hereinafter referred to as an "external board"), in general, a flexible wiring board is used. For the purpose of making devices small-sized and lightweight, a method of loading driving IC chips onto a flexible tape carrier by means of TAB (tape automated bonding) technique and connecting the tape carrier, which is used as a flexible wiring board, and an external board is widely used. In any case, such a flexible wiring board (or tape carrier) is frequently bent in actual use thereof for connecting it with an external board as arranged on the back of a display device for the purpose of attaining close contact between the connected parts with each other.
The flexibility of a conventional flexible wiring board is insufficient for using it as a bent form. Therefore, in such a conventional flexible wiring board as shown in FIG. 5, the insulator film (1) in the part to be bent is removed to form a through-hole (8b) so as to ensure the flexibility of the part before the board is bent. However, in a flexible wiring board having a through-hole through the insulator film in the part to be bent, since the conductive pattern (3) is exposed in the bent part (8), the exposed part is susceptable to short-circuiting or wire-cutting. Where a complete through-hole is formed along the whole of the part of the board to be bent, the tensile strength of the board would lower at the part having the through-hole, so that there occurs another problem that the board itself would be broken during handling.
In a conventional flexible wiring board, in general, a conductive pattern formed on an insulator film is covered with a cover layer (6) of an epoxy resist for the purpose of preventing lowering of the function of the conductor due to adhesion of dust or water to the surface of the pattern. However, the cover layer is often cracked when the board is bent so that dust or water can penetrate into the pattern through the cracks to also cause short-circuiting or breaking and corrosion of the conductor.